1. Field of the Invention
This invention relates to a mounting device for a printing head used in a thermal printer, a discharge type printer or an ink jet printer which is removably mountable to the body of such printer.
2. Description of the Prior Art
In printing mechanisms having a printing head, such as thermal printers or discharge type printers, the portion which most often needs replacement is the printing head. There are cases where the printing head must be replaced with a new one several times to several tens of times before the life of the printing mechanism body expires. Therefore, a construction which readily permits the replacement of the printing head portion is regarded as important.
Devices have heretofore been devised which are designed such that by inserting into a connector-like part a printing head to which an electrical signal is supplied, the head is regularly held and electrical connection is established. FIG. 1 of the accompanying drawings shows an example of the conventional printing head mounting and dismounting structure in a thermal printer. In FIG. 1, a carriage 1 is slidable with respect to a slide rail 2 by drive means, not shown, and the carriage 1 is movable over the entire width of the recording paper. The carriage 1 has a head connector 3 fixed thereto, and grooves 3' and 3" of the body are set so as to fit to the projected portions 5' and 5" of a thermal head 5. In the thermal head 5, reference numeral 7 designates a heating member and reference numeral 6 designates a pattern which is adapted to be in contact with the contacts 4 of the connector to transmit an electrical signal thereto. This example of the prior art readily permits replacement of the head, but it has suffered from the following serious disadvantages.
(1) Since there is no means for controlling the vertical position of the thermal head 5, the head gradually slips out of the connector during a long-time use to create a deviation of the printing position which in turn results in thinning of upper portions of printed characters. FIG. 2(A) shows a case where the head lies at its regular position, and FIG. 2(B) shows a case where the head has slipped out of the connector. In FIG. 2(A), the heating member 7 of the head 5 presses against a rubber pad 10 with recording paper 11 interposed therebetween and so, the contact between the heating member 7 and the receiving paper 11 is very good. On the other hand, in FIG. 2(B), the upper portion 7' of the heating member 7 is not pressing against the pad 10 with the recording paper 11 interposed therebetween and thus, the printed characters in this portion become extremely thin.
(2) Further, in the example of the prior art, there is some amount of backlash between the grooves 3', 3" of the connector body and the projected portions 5', 5" of the head and therefore, violent horizontal movement of the carriage 1 resulting from the printing operation causes the pattern 6 of the head 5 and the contacts 4 to slide against one another respectively. This has led to the danger that the contacts or the pattern become abraded thereby causing unsatisfactory contact therebetween.